fixes eager loading edge case in :zeitwerk mode

2 files changed, 33 insertions, 2 deletions

diff --git a/railties/lib/rails/engine.rb b/railties/lib/rails/engine.rb
index 07bd56c978..2b5afd51b8 100644
--- a/railties/lib/rails/engine.rb
+++ b/railties/lib/rails/engine.rb
@@ -567,12 +567,15 @@ module Rails
       ActiveSupport::Dependencies.autoload_paths.unshift(*_all_autoload_paths)
       ActiveSupport::Dependencies.autoload_once_paths.unshift(*_all_autoload_once_paths)
 
-      # Freeze so future modifications will fail rather than do nothing mysteriously
       config.autoload_paths.freeze
-      config.eager_load_paths.freeze
       config.autoload_once_paths.freeze
     end
 
+    initializer :set_eager_load_paths, before: :bootstrap_hook do
+      ActiveSupport::Dependencies._eager_load_paths.merge(config.eager_load_paths)
+      config.eager_load_paths.freeze
+    end
+
     initializer :add_routing_paths do |app|
       routing_paths = paths["config/routes.rb"].existent
 
diff --git a/railties/test/application/zeitwerk_integration_test.rb b/railties/test/application/zeitwerk_integration_test.rb
index c82b37d07d..e4a17e5a31 100644
--- a/railties/test/application/zeitwerk_integration_test.rb
+++ b/railties/test/application/zeitwerk_integration_test.rb
@@ -149,6 +149,34 @@ class ZeitwerkIntegrationTest < ActiveSupport::TestCase
     assert $zeitwerk_integration_test_extras
   end
 
+  test "autoload directores not present in eager load paths are not eager loaded" do
+    $zeitwerk_integration_test_user = false
+    app_file "app/models/user.rb", "class User; end; $zeitwerk_integration_test_user = true"
+
+    $zeitwerk_integration_test_lib = false
+    app_dir "lib"
+    app_file "lib/webhook_hacks.rb", "WebhookHacks = 1; $zeitwerk_integration_test_lib = true"
+
+    $zeitwerk_integration_test_extras = false
+    app_dir "extras"
+    app_file "extras/websocket_hacks.rb", "WebsocketHacks = 1; $zeitwerk_integration_test_extras = true"
+
+    add_to_config "config.autoload_paths      << '#{app_path}/lib'"
+    add_to_config "config.autoload_once_paths << '#{app_path}/extras'"
+
+    boot("production")
+
+    assert $zeitwerk_integration_test_user
+    assert !$zeitwerk_integration_test_lib
+    assert !$zeitwerk_integration_test_extras
+
+    assert WebhookHacks
+    assert WebsocketHacks
+
+    assert $zeitwerk_integration_test_lib
+    assert $zeitwerk_integration_test_extras
+  end
+
   test "autoload_paths are set as root dirs of main, and in the same order" do
     boot